HttpClientExample.java

package info.bouzuya.http_client;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.httpclient.DefaultHttpMethodRetryHandler;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpMethodBase;
import org.apache.commons.httpclient.NameValuePair;
import org.apache.commons.httpclient.methods.GetMethod;
import org.apache.commons.httpclient.methods.PostMethod;
import org.apache.commons.httpclient.params.HttpMethodParams;

public class HttpClientExample {

    public static interface Api<T> {
		public String getMethod();

		public String getPath();

		public Map<String, String> getParameters();

		public void setParameters(Map<String, String> parameters);

		public T handleResponse(int code, String body);
	}

	// post /json?k=...&p1=...&p2=...
	public static class JsonApi implements Api<String> {
		private static final String method = "post";
		private static final String pathFormat = "/json?k=%s";
		private final String pathParameter;
		private Map<String, String> parameters;

		public JsonApi(String p1) {
			this.pathParameter = p1;
		}

		@Override
		public String getMethod() {
			return method;
		}

		@Override
		public void setParameters(Map<String, String> parameters) {
			this.parameters = parameters; // FIXME
		}

		@Override
		public Map<String, String> getParameters() {
			return this.parameters; // FIXME
		}

		@Override
		public String getPath() {
			return String.format(pathFormat, pathParameter);
		}

		@Override
		public String handleResponse(int code, String body) {

			System.out.println("Response Code: " + Integer.toString(code));
			System.out.println("Response Body: " + body);

			return body;
		}
	}

	public static class Client {
		private static final int RESPONSE_BODY_MAX_LENGTH = 100 * 1024;
		private static final boolean DONT_USE_RETRY = true;
		private static final int port = 3000;

		private final String protocol;
		private final String host;
		private final String p1;

		public Client(String protocol, String host, String p1) {
			this.protocol = protocol;
			this.host = host;
			this.p1 = p1;
		}

		public String json(String p1, String p2) throws Exception {
			Api<String> api = new JsonApi(this.p1);
			Map<String, String> parameters = new HashMap<String, String>();
			parameters.put("p1", p1);
			parameters.put("p2", p2);
			api.setParameters(parameters);
			return call(api);
		}

		private <T> T call(Api<T> api) throws Exception {
			String url = protocol + "://" + host + ":" + Integer.toString(port)
					+ api.getPath();
			HttpClient client = new HttpClient();
			HttpMethodBase method = newHttpMethod(api.getMethod(), url, api
					.getParameters());
			if (DONT_USE_RETRY) {
				method.getParams().setParameter(HttpMethodParams.RETRY_HANDLER,
						new DefaultHttpMethodRetryHandler(0, false));
			}
			int code = client.executeMethod(method);
			String body = method
					.getResponseBodyAsString(RESPONSE_BODY_MAX_LENGTH);
			return api.handleResponse(code, body);
		}

		private <T> HttpMethodBase newHttpMethod(String method, String url,
				Map<String, String> parameters) {
			if (method.equals("post")) {
				PostMethod m = new PostMethod(url);
				NameValuePair[] pairs = toNameValuePairs(parameters);
				m.addParameters(pairs);
				return m;
			} else if (method.equals("get")) {
				GetMethod m = new GetMethod(url);
				NameValuePair[] pairs = toNameValuePairs(parameters);
				m.setQueryString(pairs);
				return m;
			} else {
				throw new IllegalArgumentException();
			}
		}

		private static NameValuePair[] toNameValuePairs(
				Map<String, String> parameters) {
			List<NameValuePair> paramsList = new ArrayList<NameValuePair>();
			for (Map.Entry<String, String> entry : parameters.entrySet()) {
				paramsList.add(new NameValuePair(entry.getKey(), entry
						.getValue()));
			}
			NameValuePair[] paramsArray = paramsList
					.toArray(new NameValuePair[0]);
			return paramsArray;
		}
	}

	public static void main(String[] args) throws Exception {
		Client client = new Client("http", "www.bouzuya.info", "kkk");
		String result = client.json("v1", "v2");
		System.out.println(result);

	}
}